INTRODUCTION

The material in this chapter is based on the paper by Baker and Morris (1985) on positive displacement (PD) meters, which in turn has been updated with more recent industrial and published material and extended to gases. P.D. Baker's (1983) paper provided some additional useful information on these meters. The main types of liquid meter were given by Barnes (1982), Hendrix (1982), Henke (1955), and Gerrard (1979) (cf. Mankin 1955). The reader should refer to API (1992) and similar documents.

At least four of the meter designs to be discussed have been around for over 100 years. The nutating disk flowmeter for liquids was developed in 1850. The rotary piston meter appeared in the late nineteenth century (Baker 1998).

The measurement of gas has depended, from an early date, on two types of positive displacement meter: the wet gas meter of high accuracy and credited to Samuel Clegg (1815), and the diaphragm meter of lower performance but greater range for which William Richards (1843) should take the credit.

BACKGROUND

The concept of carrying known volumes of fluid through a flowmeter is a short step from the use of a discrete measure such as a bucket or measuring flask. Thus in each of the designs described later, the flow enters a compartment that is as tightly sealed as is compatible with relative movement of adjacent components.